A person who is authorized to perform business-related transactions on behalf of someone else (the principal). In order to become someone's attorney in fact, a person must have the principal sign a power of attorney document. This document designates the person as an agent, allowing him or her to perform actions on the principal's behalf.

The extent of the power of attorney document determines the amount of responsibility that the attorney in fact possesses. Attorneys in fact operate under general power of attorneys, meaning that they are not restricted and can represent their principals in any transaction. In the case of a special power of attorney, the attorney in fact has restricted powers and can represent the principal in specific situations.